Simultaneous Measurement of Intracrystalline Diffusion in Molecular Sieve Zeolites by NMR and Gravimetric Methods

研究综述：用重量法和核磁共振法研究了烃类在高硅沸石上的扩散和吸附性质，以解决扩散测量中的差异，文献中报道这两种技术的测量结果相差几个数量级，以便对分子筛中的扩散有基本的了解。新颖性：一种新的仪器正在建造中，将使用核磁共振和重量分析方法，在完全相同的条件下，在相同的山梨醇压力下，对相同的沸石样品进行同时扩散测量。这种独特的测量方法将有可能将微观核磁共振测量的结果与宏观重力测量的结果进行比较，从而解决目前存在的巨大差异。技术影响：从拟议工作中获得的信息不仅将提供对沸石传输和吸附性质的基本了解，而且将对改进诸如气流净化、分离过程和催化转化装置等重要操作的工程设计具有重要意义。了解择形沸石的扩散机理和平衡性质，可以为了解择形沸石在二甲苯异构化、脱蜡和甲醇转化为汽油等实际工业应用中的催化行为提供有价值的信息。

Research Summary: The diffusive and adsorptive properties of hydrocarbons on high-silica zeolites are investigated by gravimetric and NMR methods to resolve the differences in diffusion measurements, which are reported in the literature to be of several orders of magnitude between measurements made by these two techniques, in order to gain fundamental understanding of diffusion in zeolites. Novelty: A new apparatus is being constructed and will be used to make simultaneous diffusion measurements of identical zeolite samples, activated under exactly the same conditions, under identical sorbate pressure, using NMR and gravimetric methods. This unique method of measurement will make it possible to compare the results from microscopic NMR measurements to those from macroscopic gravimetric measurements, thus resolving currently existing large differences. Technical Impact: The information obtained from the proposed work will not only provide fundamental understanding of the transport and adsorption properties of zeolites but also will be of importance in improving engineering design in such important operations as purification of gas streams, separation processes, and catalytic conversion units. A better understanding of the diffusion mechanisms and equilibrium properties can provide valuable information in understanding catalytic behavior of shape-selective zeolites used in practical industrial applications such as xylene isomerization, dewaxing and conversion of methanol to gasoline.